(function(window, document) {
  'use strict';

  var html = document.documentElement || document.querySelector('html');
  function resetFontSize() {
    var width = html.getBoundingClientRect().width;
    // // 设置页面最小宽度
    if (width <= 400) width = 400;
    html.style.fontSize = (width / 1920) * 16 + 'px';
  }
  resetFontSize();
  window.addEventListener('resize', resetFontSize, false);
})(window, document);

var SEPARATION = 100,
  AMOUNTX = 50,
  AMOUNTY = 50;

var container;
var camera, scene, renderer;

var particles,
  particle,
  count = 0;

var mouseX = -660,
  mouseY = -510;

var windowHalfX = window.innerWidth / 2;
var windowHalfY = window.innerHeight / 1;

window.onload = function () {
  init();
  animate();
}

function init() {
  container = document.createElement('div');
  container.id = 'banner-canvas';
  container.style = "position:absolute;top:0;left:0;";
  document.getElementById('particles').appendChild(container);
  camera = new THREE.PerspectiveCamera(
    75,
    window.innerWidth / window.innerHeight,
    1,
    10000
  );
  camera.position.z = 1000;

  scene = new THREE.Scene();

  particles = new Array();

  var PI2 = Math.PI * 2;
  var material = new THREE.ParticleCanvasMaterial({
    color: '#007ec6',
    program: function(context) {
      context.beginPath();
      context.arc(0, 0, 1, 0, PI2, true);
      context.fill();
    },
  });

  var i = 0;

  for (var ix = 0; ix < AMOUNTX; ix++) {
    for (var iy = 0; iy < AMOUNTY; iy++) {
      particle = particles[i++] = new THREE.Particle(material);
      particle.position.x = ix * SEPARATION - (AMOUNTX * SEPARATION) / 2;
      particle.position.z = iy * SEPARATION - (AMOUNTY * SEPARATION) / 2;
      scene.add(particle);
    }
  }

  renderer = new THREE.CanvasRenderer();
  renderer.setSize(window.innerWidth, window.innerHeight);
  container.appendChild(renderer.domElement);

  document.addEventListener('mousemove', onDocumentMouseMove, false);
  window.addEventListener('resize', onWindowResize, false);
}

function onWindowResize() {
  windowHalfX = window.innerWidth / 2;
  windowHalfY = window.innerHeight / 2;
  camera.aspect = window.innerWidth / window.innerHeight;
  camera.updateProjectionMatrix();
  renderer.setSize(window.innerWidth, window.innerHeight);
}

function onDocumentMouseMove(event) {
  mouseX = event.clientX - windowHalfX;
  if (event.clientY <= 650) {
    mouseY = event.clientY - windowHalfY;
  }
}

function onDocumentTouchStart(event) {
  if (event.touches.length === 1) {
    event.preventDefault();
    mouseX = event.touches[0].pageX - windowHalfX;
    mouseY = event.touches[0].pageY - windowHalfY;
  }
}

function onDocumentTouchMove(event) {
  if (event.touches.length === 1) {
    event.preventDefault();
    mouseX = event.touches[0].pageX - windowHalfX;
    mouseY = event.touches[0].pageY - windowHalfY;
  }
}

function animate() {
  requestAnimationFrame(animate);
  render();
}

function render() {
  camera.position.x += (mouseX - camera.position.x) * 0.05;
  camera.position.y += (-mouseY - camera.position.y) * 0.05;
  camera.lookAt(scene.position);
  var i = 0;
  for (var ix = 0; ix < AMOUNTX; ix++) {
    for (var iy = 0; iy < AMOUNTY; iy++) {
      particle = particles[i++];
      particle.position.y =
        Math.sin((ix + count) * 0.3) * 50 + Math.sin((iy + count) * 0.5) * 50;
      particle.scale.x = particle.scale.y =
        (Math.sin((ix + count) * 0.3) + 1) * 2 +
        (Math.sin((iy + count) * 0.5) + 1) * 2;
    }
  }
  renderer.render(scene, camera);
  count += 0.08;
}
